There are three main types of non-electrical insect control devices or methods: entrapment, contact poison, or ingested poison. Entrapment helps control a current population of insects in a location, as do either contact or ingested poisons of the "quick kill" variety. Complete destruction of a source of insects can only be achieved by the use of a "delayed-kill" toxicant which aggregating insects will carry back to their home colony.
The use of such a "delayed kill" bait-toxicant formulation for the eradication of colonies of wasps is disclosed by and discussed in U.S. Pat. No. 5,152,992 to Kandathil et al., "Method for Control of Social Insects with a Hemisalt of a Perfluroalkane Sulfonic Acid". The bait-toxicant formulation disclosed by this patent is a concentration dependent toxicant formulation. The toxicant level is kept low enough so that foraging wasps are not immediately killed by the amount of toxicant, so they are able to carry portions of the formulation back to their home colony and share it with wasps inside the colony. As the wasps ingest more of the formulation, the toxicant level builds up to lethal levels. Ultimately, the whole colony is destroyed.
One problem with insect control methods involving toxicants that must be ingested is that the toxicant must be eaten by the target insect. For this reason, toxicants are almost always blended with a bait which is attractive to the target insect. While this may sound simple and fundamental, many parameters must be balanced to provide an effective bait-toxicant formulation, and differences in feeding preferences and sensitivities in different species of target insects.
Roaches may be described as feeding "source generalists." They will eat almost anything unless the food source has too high an adulterant level of toxicant, surfactant, or other substance that makes them consider the food not palatable. Thus, getting roaches to eat the bait-toxicant formulation does not present much of a problem.
When the target insect is a wasp, however, there is a problem. Wasps are also feeding source generalists, but are quite sensitive to the presence of adulterants in the food. A palatable bait toxicant formulation, carefully prepared so that the levels of toxicants and surfactants are kept low enough that the wasps would ingest the formulation was disclosed in U.S. Pat. No. 5,152,992. Such a formulation could be dispersed by any type of liquid dispersing station.
Devices that allow liquid to travel up a wick from a reservoir are well known, and range from kerosene lamps to the old AIRWICK air fresheners. An example of the use of a wicking mechanism used in an insect control device is disclosed by U.S. Pat. No. 1,916,982 to Jones, "Fly Destroyer." A fly poison mixed with sugar is placed in contact with an absorbent pad which extends into a sealable liquid reservoir. The user fills the reservoir with water, which wets the pad, and flies landing on the device are then offered a poisoned sugar solution.
Devices that allow liquid to be dispensed downwardly from a tube extending from a reservoir are also well known and can be seen attached to the rodent cages in any pet store. One device that allows the controlled gravity feed dispensing of a toxic liquid is disclosed by U.S. Pat. No. 2,860,445 to Yates, "Rodent Exterminating Device" discloses a dispensing apparatus having a liquid container which gravity feeds into a feed pipe. When the liquid reaches a predetermined level in a liquid well beneath the container, a floating ball check valve closes off the feed pipe and prevents further flow.
One entrapment type trap which the user must activate by adding the bait lure as well as water to drown the attracted yellowjackets, marketed as the "Deluxe Surefire Yellowjacket Wasp Trap" is manufactured by Consep Membranes Inc.
A liquid bait station intended to be used for the control of crawling insects such as roaches having a single reservoir portion which fits within a base structure is disclosed by U.S. Pat. No. 5,033,229 to Demarest et al. A liquid bait-toxicant formulation is released from the reservoir onto and moistens an absorbent pad. Insects can, through peripheral openings in the base structure, access the bait-toxicant soaked pad, feed therefrom, and, ultimately die.
U.S. Pat. No. 5,152,992, discussed earlier, discloses the use of a generic reservoir with a wicking mechanism from which wasps or other flying insects may feed to ingest a delayed-action bait-toxicant solution which has been formulated to be palatable to the wasps.
An approach to getting yellowjackets to ingest a toxicant that has been found very effective might be called "bait and switch." If the yellowjackets have been allowed to become accustomed to a liquid food source containing no toxicants (a bait-only formulation), they are more likely to continue feeding from the source after a toxicant is added to the formulations. For such a method to be convenient and effective, a specialized delivery system needs to be employed.